Glassware forming machines of the individual section type are well known and comprise a number of individual glassware forming units (known as sections) which receive gobs of molten glass from a common source and feed their output to a common conveyor. Each section has a mould arrangement which operates to form parisons and a further mould arrangement which operates to blow the parisons into the shape of glassware containers. Conventional machines of the individual section type have various members which, in the operation of the machine, are moved between operative and out-of-the-way positions thereof along a path which has a vertical component and an arcuate component about a vertical axis. Thus, the member swings into alignment with parts with which it co-operates as it is moved downwardly towards those parts. Such members are the funnels used to guide gobs of molten glass to the parison mould arrangement of a section, baffles which are used to close top portions of the moulds of the parison mould arrangement, and blow heads which are used to blow air into parisons at the blow mould arrangement of the section. For example, a blow head is moved from a position out of alignment with a mould and above the mould along a path which by a combination of vertical downwards movement and swinging movement about a vertical axis brings the blow head into engagement with the mould. In conventional individual section type machines, the members are moved along such paths by fluid-pressure operated moving mechanisms each comprising a vertically-extending cylinder, a piston movable vertically in the cylinder upon the introduction of fluid under pressure into the cylinder, a first piston rod projecting from said piston along said vertical axis, the member being mounted on the first piston rod for movement therewith, a second piston rod projecting from said piston in the opposite direction to said first piston rod, and cam means acting on the second piston rod to cause it to turn about the vertical axis as it moves vertically. Thus, the piston and the first piston rod are turned about the vertical axis and the member is moved arcuately about the vertical axis. The cam means comprises a cam track extending adjacent to the second piston rod and a cam follower in the form of a roller which is mounted on the second piston rod and engages the cam track. In some cases, the cam means can act on the first piston rod so that the second piston rod is not required.
Where machines of the individual section type are operated by electronic control means which acts to provide impulses which cause the introduction of fluid under pressure into the cylinders of moving mechanisms of the machine either above or below the piston, it has been recognised that it is desirable to provide feedback to the control means relating to the time of arrival of the members in their operative or out-of-the-way positions. If this is done, it is possible to ensure that any slow-acting mechanisms are compensated for by allowing an earlier operating impulse therefor. Furthermore, it is not necessary to allow extra time for the mechanism to reach its operative or out-of-the-way positions in order to prevent collisions between various parts of the machine but instead the cycle time of the machine can be decreased thereby giving greater production. However, difficulties arise in detecting movement of such members because the environment in which the member moves is generally hostile to electronic detectors because of the presence of molten glass and/or excessive heat in this environment.
It is an object of the present invention to provide a method of monitoring the movement of a member of the type described above in which method proximity detectors can be used.